Katy Perry

"The people have the power! Proud to stand by you for 4 more years. RT @BarackObama This happened because of you. Thank you"

Mitt Romney

Mitt Romney, the losing Republican candidate, showed he was a good sport when he came out to congratulate Obama and his supporters:

"I wish all of them well, but particularly the President, the First Lady and their daughters. This is a time of great challenges for America, and I pray that the President will be successful in guiding our nation."

Lady Gaga

Another one of the president's famous supporters, Lady Gaga posted this message online:

"I JUST GOT OFF STAGE IN COLUMBIA!! CONGRATULATIONS MR. PRESIDENT @BarackObama We are so proud to be American tonight! YES!!! YES! YES"

Angela Merkel

The Chancellor of Germany said she looked forward to continuing working with Mr Obama:

"I would like to heartily congratulate re-elected President Barack Obama. We know each other well and I look forward to our cooperation... (in the relationship) between Europe and the United States of America."